This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The VBD core has continued to maintain an Anopheles stephensi colony, which is used to transmit Plasmodium cynomolgi, a model of human vivax malaria, to rhesus macaques. The tick colony has continued to be instrumental in enabling our division to do research in Lyme borreliosis using the natural mode of infection. The technique of capillary feeding of nymphal ticks, which we have available, allows us to infect ticks with spirochetal clonal isolates. This is often essential to ensure defined host-responses to infection. We also are able to infect larval ticks by immersion in tissue-culture fluid that contains spirochetes. The tick section of the core has currently available numerous specimens of all of the developmental stages of Ixodes scapularis. Larvae, nymphs, and adults are stored at 4[unreadable]C in a staggered fashion. Therefore, we usually have all of the stages available at most times throughout the year. This includes 5-10 jars of larvae (with about 1000 larvae each) and several hundred uninfected nymphs for experimental needs as they arise. We have continued our collaboration with the University of Texas Health Sciences Center, Houston, TX, on the identification of virulence determinants of B. burgdorferi the affect infectivity of spirochetes to ticks, and to mice via ticks. This year 102 adult females were collected and were blood fed. A total of 68 of those fed successfully, and 33 of those laid eggs. The number of larvae that fed and were collected were 1913, and 1749 of those successfully molted into nymphs to be used in future experiments. A total of 223 nymphs were capillary-fed successfully. Those ticks were used in 2 large experiments. The remainder of the nymphs will be used in the current year.